In this article, we will share short notes for GATE Mechanical Engineering on the topic of planar supports which can be used to solve many questions on beams in the subject of Strength of Materials.

The main problem is to find reactions, which are forces and moments exerted on a body (mostly a beam) by its supports.

1) Pin support

The figure below shows pin support. There is a beam which is attached by a pin to a bracket. The beam is free to rotate about the axis of the pin. The translation of the beam with respect to the bracket is not possible as the support exerts a reaction that prevents this movement.

The pin support can exert a force in any direction and this kind of support is not capable of exerting a couple.

and are the reactions.

2) Roller support

The figure below shows pin support mounted on rollers. The roller support is only capable of exerting a normal (perpendicular) force to the surface on which the roller support moves freely.

The roller support is not capable of exerting a couple about the axis of the pin, and it cannot exert a force parallel to the surface on which it is translating.

3) Fixed support

The figure below shows a fixed or a built-in support. A fixed support is capable of exerting two components of force and a couple.